Gold Colloid

• BBI particles are proven stable for at least 24 months and are supplied with a minimum of three month’s expiry. Stable particles ensure a settled testing regime, saving you time and wastage
• Uniform shape and standard size with a low coefficient of variation. This ensures even antibody loading giving reliable results in your assay.
• Manufacturing scale. Batch sizes of up to 350+ litres to ensure you have a continuous supply.

No. BBI’s gold colloids and conjugates are not suitable for injection, administration by mouth or any other in-vivo application. The products are supplied for in vitro use only, to be used for research and/or further manufacturing purposes, and not for use in humans or animals. 
 
Any use of the products for off-label, in-vivo applications is strictly done at the customer’s own risk. BBI does not accept responsibility for the misuse of any of its products. 

The exact method is proprietary; however, it can be shared that the gold nanoparticles are formed by the citrate reduction of a gold chloride solution. 

The gold nanoparticles are formed by the citrate reduction of a gold chloride solution. This leaves the gold particles with a citrate shell, which confers a net negative charge upon the particles, allowing them to repel each other and remain in solution. No other stabilising agents or preservatives are added to the gold colloid following the manufacturing process. 

No. Frozen colloids precipitate and become clear in colour with visible aggregates present. This process is irreversible. Ideally, colloids should be stored in the door of a fridge or away from the chillers in a cold room to prevent accidental freezing.

BBI offers more concentrated versions of the 20nm and 40nm gold colloids, referred to as the HD Grade range. In addition to the standard concentration (OD520 1) products, OD520 5 (20nm only) and OD520 10 (20nm and 40nm) products are available in 10ml and 50ml pack sizes. HD Grade gold colloids do not have an expiry date applied to them as BBI has not carried out a stability study on this product range. The batch size of the product range is limited to 50ml. For these reasons, the HD Grade colloid range is not suitable for use in the making of gold conjugates for lateral flow test manufacture or any other kind of regulated manufacture. 

Gold nanoparticles ≥40nm in diameter will sink out of solution and settle at the bottom of their container. Colloids that have settled in this way can be resuspended by inversion. 

BBI’s gold colloid is manufactured at our ISO 13485:2015 certified facility in Crumlin, South Wales, UK. 

• BBI particles are proven stable for at least 24 months and are supplied with a minimum of three month’s expiry. Stable particles ensure a settled testing regime, saving you time and wastage. 

• Uniform shape and standard size with a low coefficient of variation. This ensures even antibody loading giving reliable results in your assay. 

• Manufacturing scale. Batch sizes of up to 350+ litres to ensure you have a continuous supply. 

If the gold colloid is to be diluted for use, it is recommended to use purified water of a comparable purity (resistivity ≥18MΩ) to that used in the manufacture process 

The risk of the colloids freezing far outweighs the risk of the colloids being exposed to elevated temperatures. If the colloid freezes (even if only for a short time), it will irreversibly collapse. In contrast, the colloids tolerate being exposed to elevated temperatures well for a short period of time. 
 
We do recommend that the colloid is kept at 2-8°C for long term storage, however over a short period of time (such as a few days, which will be the case during international shipping) the 
colloid will be fine at higher temperatures. Adding cold packs to the shipping carton will increase the risk of freezing, and should be avoided. 

BBI have assigned an expiry date to the product based on our real time stability studies. The studies did not test the colloid to the point of failure. It is therefore possible that, if the product has been stored and handled correctly, the material could be successfully used after the expiry date. As the product is beyond the recommended BBI expiry, the performance stated on the Certificate of Analysis is not guaranteed, and the product would need to be assessed to ensure it is still meeting the requirements of the specific application. 

The gold colloid will remain stable until at least the expiry date stated on the label if the colloid is kept unopened at the recommended storage temperature (2-8°C). BBI’s EM Grade gold colloids are assigned a 24-month expiry date from the date of manufacture. Stability was ascertained by real-time stability studies for the shelf life of the product. 

BBI GC5-80nm all have an Optical density (OD) stated on the Certificate of Analysis; these will be read in a UV-Vis spectrophotometer at A520nm. For particle sizes above 80nm, the peak of the spectral wavelength becomes more poorly defined. It is therefore hard to ascertain a consistent wavelength at which to read the OD from batch to batch. 

For best results (to help avoid particle aggregation) the end-user should avoid pipetting directly from the bottle. Instead they should pour out a small aliquot into a suitable container 
(borosilicate glass is recommended) and pipette from this. This protects the bulk solution from cross-contamination and potential introduction of particulate matter (such as dust) which can cause particle aggregation. It is recommended that the bulk volume of gold colloid be kept in its original container. 

The smallest gold nanoparticle that BBI offers is 5nm in diameter and the largest is 250nm. The particle sizes available are: 5nm, 10nm, 15nm, 20nm, 30nm, 40nm, 50nm, 60nm 80nm, 100nm, 150nm, 200nm and 250nm.

The gold nanoparticles are provided suspended in purified water (as made), with only residual chemicals left from manufacture also present in solution.